Quality of Service (QoS) may refer to the transport of network traffic with special requirements relating to the quality of the network connection. The special requirements may relate to the ability to provide different applications, users, or data flows, with different levels of service. For example, a particular level of QoS may guarantee a required bit rate, delay, jitter, packet dropping probability, and/or bit error rate. QoS guarantees can be important when the network capacity is insufficient or burdened. Certain applications, such as real-time streaming multimedia applications (e.g., voice over IP) may require, in order to be useful to the end-user, a higher QoS guarantee, while other applications, such as ones related to the downloading of a file, may be effective with QoS guarantees corresponding to a lower level of network service.
A network that supports QoS may include one or more network devices that process network traffic. Each of the network devices may include a packet scheduler. Each packet scheduler may, based on priorities assigned to packets, schedule the packets for transmission from the network device. Existing packet schedulers may schedule network traffic based on the relative priorities of the network traffic.